There must be a problem with double sides or with normals in the Mantle Clock.
When you remove normals from OBJ files (remove the last [font=courier new]/vindex[/font] in the triplets of the lines starting by [font=courier new]f[/font]), or when you import / reexport the model in Blender, the parts of the clock which are rendered in black aren't black anymore.
Which software was used to design it?